Medium feeding apparatus and image reading apparatus

ABSTRACT

A medium feeding apparatus includes a curved path that is a medium feeding path formed between a first pair of feeding rollers and a second pair of feeding rollers. The medium is transported along the curved path while being curved downward. The medium feeding apparatus further includes an accommodating portion formed outside a curve of the curved path and configured to accommodate a deformed part of the medium at the curved path. The first pair of feeding rollers is provided at a center area in a medium width direction intersecting with a medium feeding direction. The accommodating portion has a pushing member configured to push the deformed part of the medium upstream in the medium feeding direction.

The present application is based on, and claims priority from JPApplication Serial Number 2018-144075, filed Jul. 31, 2018, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

Embodiments of the present disclosure relate to a medium feedingapparatus and an image reading apparatus equipped therewith.

2. Related Art

Scanners, printers and the like are equipped with a medium feedingapparatus that feeds a medium. For example, in scanners, a mediumfeeding apparatus is sometimes called as ADF, which is an acronym forAutomatic Document Feeder. Some ADFs have a curved path structure for,after a pickup feed of a sheet of medium, transporting the medium alongits curve downward to turn over the medium. An example of an ADF thathas such a structure is disclosed in JP-A-8-34544.

In some ADFs, a skew is corrected by performing registration of theleading edge of a medium into alignment with a pair of resist rollers.In the skew correction process, ridge-like partial deformation occurs inthe curved part of the medium. In JP-A-8-34544, the term “loop” is usedfor referring to the curved part of the medium, and the term “bulge” isused for referring to the ridge-like deformed part mentioned above. TheADF disclosed in JP-A-8-34544 has a pivotable guide member that pushesthe bulge. This structure pushes the leading edge of the medium for edgeregistration into alignment with the pair of resist rollers.

When the leading edge of a medium that is skewed reaches a pair ofresist rollers, the degree of deformation of a deformed part at one sidethat reaches the pair of resist rollers earlier than the opposite sidein the width direction of the medium because of the skew tends to begreater than the degree of deformation of a deformed part at theopposite side that reaches the pair of resist rollers later. Thefollowing is a detailed explanation of this phenomenon. The upper partof FIG. 9 depicts an example of a state before the leading edge of amedium D transported toward the bottom of FIG. 9 reaches a resist rollerpair 100, wherein, as illustrated therein, the medium D is skewed, thatis, inclined with respect to a virtual line Lv that is in parallel witha transportation direction.

The leading edge at one side S1 of the medium in its width directionreaches a resist roller pair 100 earlier than the leading edge at theopposite side S2 because of the skew, and the degree of deformation of adeformed part H1 produced by subsequent transportation at the one sideS1 tends to be greater than the degree of deformation of a deformed partH2 produced by subsequent transportation at the opposite side S2. To beexact, “the degree of deformation is greater” means that the deformedpart is larger both in the transportation direction and in the heightdirection, in most cases.

The pivotable guide member disclosed in JP-A-8-34544 has a pivot locatedupstream in the transportation direction, and, if the pivotable guidemember disclosed in JP-A-8-34544 is applied to the example illustratedin FIG. 9, the deformed part H1 and the deformed part H2 are pushedtoward the resist roller pair 100. However, if this structure is used,it is impossible to perform proper skew correction because the deformedpart H1, which is at the side that arrives earlier due to the skew, ispushed excessively and because a force of pushing the deformed part H2,which is at the side that arrives later due to the skew and is supposedto be pushed hard for the purpose of skew correction, tends to beinsufficient.

SUMMARY

A medium feeding apparatus according to an aspect of the presentdisclosure includes: a first pair of feeding rollers configured to feeda medium downstream; a second pair of feeding rollers provideddownstream of the first pair of feeding rollers; a curved path that is amedium feeding path formed between the first pair of feeding rollers andthe second pair of feeding rollers, the medium being transported alongthe curved path while being curved downward; and an accommodatingportion formed outside a curve of the curved path and configured toaccommodate a deformed part of the medium at the curved path; whereinthe first pair of feeding rollers is provided at a center area in amedium width direction intersecting with a medium feeding direction, andwherein the accommodating portion has a pushing member configured topush the deformed part of the medium upstream in the medium feedingdirection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a medium feeding apparatus and an imagereading apparatus according to an exemplary embodiment of thedisclosure.

FIG. 2 is a side sectional view of a medium feeding apparatus and animage reading apparatus according to an exemplary embodiment of thedisclosure.

FIG. 3 is a block diagram that illustrates a control system in a mediumfeeding apparatus and an image reading apparatus according to anexemplary embodiment of the disclosure.

FIG. 4 is an enlarged side sectional view of a part of a medium feedingpath in a medium feeding apparatus according to an exemplary embodimentof the disclosure.

FIG. 5 is an enlarged side sectional view of a part of a medium feedingpath in a medium feeding apparatus according to an exemplary embodimentof the disclosure.

FIG. 6 is an enlarged plan view of a part of a medium feeding path in amedium feeding apparatus according to an exemplary embodiment of thedisclosure.

FIG. 7 is an enlarged side sectional view of a part of a medium feedingpath in a medium feeding apparatus according to an exemplary embodimentof the disclosure.

FIG. 8 is a flowchart that illustrates the flow of control performedwhen a medium is fed.

FIG. 9 is an enlarged plan view of a part of a medium feeding path in amedium feeding apparatus according to related art.

FIG. 10 is an enlarged side sectional view of a part of a medium feedingpath on which a pushing member is not provided.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following is a brief overview of the present disclosure. A mediumfeeding apparatus according to a first aspect of the present disclosureincludes: a first pair of feeding rollers configured to feed a mediumdownstream; a second pair of feeding rollers provided downstream of thefirst pair of feeding rollers; a curved path that is a medium feedingpath formed between the first pair of feeding rollers and the secondpair of feeding rollers, the medium being transported along the curvedpath while being curved downward; and an accommodating portion formedoutside a curve of the curved path and configured to accommodate adeformed part of the medium at the curved path; wherein the first pairof feeding rollers is provided at a center area in a medium widthdirection intersecting with a medium feeding direction, and wherein theaccommodating portion has a pushing member configured to push thedeformed part of the medium upstream in the medium feeding direction.

In this aspect, the accommodating portion configured to accommodate adeformed part of the medium is provided at the curved path, and thefirst pair of feeding rollers is provided at the center area in themedium width direction intersecting with the medium feeding direction.This structure allows the bulge of the deformed part to escape upstreamin the feeding direction from the lateral side of the first pair offeeding rollers and ensures easy rotation of the medium turning on theportion of contact with the first pair of feeding rollers, therebymaking it easier to correct the skew. Since the accommodating portionhas the pushing member configured to push the deformed part of themedium upstream in the medium feeding direction, the medium is rotatedon the portion of contact with the first pair of feeding rollers, andthe skew is therefore corrected well. If the pushing member is notprovided, the medium tends to cling to the outer portion of the curvedpath. The clinging makes it harder for the medium to rotate, that is,makes it harder to correct the skew. Since the pushing member isprovided, the pushing member fulfills a function of separating themedium from the wall surface thereof. This is another reason why theskew is corrected well.

In the first aspect, the pushing member may be an elastic member whosedownstream portion in the medium feeding direction is fixed and whoseupstream portion in the medium feeding direction pushes the deformedpart of the medium. In this mode, since the pushing member is an elasticmember whose downstream portion in the medium feeding direction is fixedand whose upstream portion in the medium feeding direction pushes thedeformed part of the medium, it is possible to push the deformed part ofthe medium upstream in the medium feeding direction properly.

In the first aspect, the pushing member may be a pivot member that has apivot at a downstream portion in the medium feeding direction, and anupstream portion located upstream of the pivot in the medium feedingdirection pushes the deformed part of the medium. In this mode, sincethe pushing member is a pivot member that has a pivot at a downstreamportion in the medium feeding direction, and since an upstream portionlocated upstream of the pivot in the medium feeding direction pushes thedeformed part of the medium, it is possible to push the deformed part ofthe medium upstream in the medium feeding direction properly.

In the first aspect, the pushing member may be provided at a center areain the medium width direction. In this mode, since the pushing member isprovided at a center area in the medium width direction, it is easierfor the force of pushing the medium by the pushing member to equally actat one side and the opposite side in the medium width direction, andthus it is possible to correct the skew properly even if it is notpredictable which one of the two in the medium width direction will bethe side where the degree of deformation is greater.

The medium feeding apparatus according to the first aspect may furtherinclude a controller configured to control the first pair of feedingrollers and the second pair of feeding rollers; wherein the controllerchanges an amount of driving the first pair of feeding rollers dependingon feeding conditions when the first pair of feeding rollers is driven,with the second pair of feeding rollers stopped.

In this mode, since the controller configured to control the first pairof feeding rollers and the second pair of feeding rollers changes anamount of driving the first pair of feeding rollers depending on feedingconditions when the first pair of feeding rollers is driven, with thesecond pair of feeding rollers stopped. Therefore, it is possible tocorrect the skew suitably in accordance with the feeding conditions.

An image reading apparatus according to a second aspect of the presentdisclosure includes: a reader configured to read a medium; and themedium feeding apparatus according to the first aspect configured tofeed the medium toward a reading position where the medium is read bythe reader. With this aspect, the same operational effects as thosedescribed above can be obtained in the image reading apparatus.

Embodiments of the present disclosure will now be explained in detail.Described below with reference to the accompanying drawings are a mediumfeeding apparatus according to an exemplary embodiment of the disclosureand an image reading apparatus equipped therewith. In the descriptionbelow, a scanner 10 is taken as an example of the image readingapparatus. In the X-Y-Z coordinate system depicted in each drawing, theX direction corresponds to the width direction of a medium transportedinside the apparatus. The Z direction corresponds to the heightdirection of the apparatus and to the vertical direction. The Ydirection is orthogonal to the X direction and the Z direction. The −Xdirection is defined as a direction toward the front of the apparatus.The +X direction is defined as a direction toward the rear of theapparatus.

As illustrated in FIG. 1, the scanner 10 is provided over a recordingunit 2 and is configured as a component of a multifunction peripheral 1that has both a recording function and an image reading function. Asillustrated in FIG. 2, the scanner 10 includes a scanning unit 11 and amedium feeding apparatus 12. The scanning unit 11 includes a readingdevice 16 that reads a document set on a document table 14. The mediumfeeding apparatus 12 feeds sheets of a document stacked on a feedingtray 20 toward the reading device 16. The document is hereinafterreferred to as medium P.

The medium feeding apparatus 12 is switchable between a closedpositional state and an open positional state. The document table 14(FIG. 2) of the scanning unit 11 is covered when the medium feedingapparatus 12 is closed as indicated by solid-line illustration inFIG. 1. The document table 14 of the scanning unit 11 is not coveredwhen the medium feeding apparatus 12 is open as indicated by dotted-lineillustration in FIG. 1. More specifically, the medium feeding apparatus12 is connected to the scanning unit 11 such that it can be opened awayfrom and closed toward the scanning unit 11, wherein the pivot of itsopening operation and closing operation exists near the +X directionalend of the scanning unit 11.

An operation unit 6 is provided on the front portion of themultifunction peripheral 1. The operation unit 6 includes a display suchas a liquid crystal display panel. By operating the operation unit 6, auser is able to input, into the multifunction peripheral 1, instructionsfor recording operation performed by the recording unit 2 and imagereading operation performed by the scanner 10.

In the multifunction peripheral 1, a plurality of sheet cassettes 3containing sheets of printing paper are provided under the recordingunit 2. A printer device 4 that performs recording on the medium P thatis transported is provided inside the recording unit 2. Recording isperformed on the medium sheet transported from the sheet cassette 3.After recording, the recorded sheet is ejected from an ejection port 7.In the multifunction peripheral 1, the ejection port 7 is providedbetween the scanner 10 and the sheet cassettes 3 as viewed in the Zdirection, that is, the apparatus height direction. An ejection tray 5receives each sheet ejected from the ejection port 7 after recording.

In FIG. 2, for example, an optical reading device conforming to a CISimaging format or a CCD imaging format is used as the reading device 16of the scanning unit 11. The reading device 16 is provided under thedocument table 14, is capable of moving in the Y direction, and iscapable of reading a medium set on the document table 14. The documenttable 14 is made of, for example, colorless transparent glass.

A holder plate 15 for holding the medium P set on the document table 14is provided on the bottom of the medium feeding apparatus 12 illustratedin FIG. 2. The document table 14 becomes exposed when the medium feedingapparatus 12 is opened. A user places a sheet of medium P on thedocument table 14, closes the medium feeding apparatus 12 to hold themedium P with the holder plate 15, and gives a scanning instruction forcausing the reading device 16 to move in the Y direction, with themedium P held. It is possible to scan the medium P in this way. Thescanner 10 is capable of not only scanning the medium P set manually onthe document table 14 but also scanning the medium P fed by the mediumfeeding apparatus 12.

With reference to FIG. 2, the medium feeding apparatus 12 will now beexplained. In FIG. 2, the dashed dotted line denoted as T represents amedium feeding path in the medium feeding apparatus 12. The mediumfeeding path T is a path leading to an ejection tray 39 from a pickupposition where the medium P is grabbed by a pick roller 21 describedbelow.

As illustrated in FIG. 2, sheets of the medium P to be fed by the mediumfeeding apparatus 12 are stacked on the feeding tray 20. That is, thefeeding tray 20 is a medium setting portion on which the medium P beforefeeding is set. The medium P to be fed is picked up by the pick roller21 from the feeding tray 20. The pick roller 21 is provided at a regioncorresponding to the +Y side of sheets of the medium P stacked on thefeeding tray 20, that is, at a position facing the leading-edge part ofthe medium P in a feeding direction. A feeding roller 22 is providedrelatively at the +Y side downstream of the pick roller 21 in thefeeding direction. In other words, the pick roller 21 is locatedupstream of the feeding roller 22 in the feeding direction.

The pick roller 21 is able to change its position between a position ofbeing in contact with the medium P and a position of being not incontact with the medium P. The pick roller 21 draws out the medium Ptoward the feeding roller 22 by rotating in the contact state. The pickroller 21 is attached to a holder 27 that operates coaxially with thefeeding roller 22. The pick roller 21 rotates by receiving motive powerfrom a first motor 63 (FIG. 3).

The feeding roller 22 feeds the medium P picked up by the pick roller 21downstream. The feeding roller 22 rotates by receiving motive power fromthe first motor 63 (FIG. 3).

A separation roller 23 is provided opposite and beneath the feedingroller 22. A rotational torque of a second motor 64 (FIG. 3) istransmitted to the separation roller 23. In addition, a predeterminedrotation resistance is applied to the separation roller 23 by a torquelimiter that is not illustrated. Although a rotational torque that actsin a reverse rotation direction of returning the medium P upstream(clockwise direction in FIG. 2) is transmitted to the separation roller23 from the second motor 64 (FIG. 3), during document feeding operation,the separation roller 23 rotates as a follower roller in a forwardrotation direction of feeding the medium P downstream (counterclockwisedirection in FIG. 2) against the reverse rotational torque due to theaction of the torque limiter when there is no medium P between theseparation roller 23 and the feeding roller 22 or when there is onesheet only of the medium P between the separation roller 23 and thefeeding roller 22.

If two or more sheets of the medium P enter the nip between theseparation roller 23 and the feeding roller 22 together in amultiple-fed one-on-the-other state, the separation roller 23 rotates inthe reverse rotation direction of returning the medium P upstreambecause of the reverse rotational torque described above. This preventsmultiple feeding of the medium P from occurring.

Next, an acceleration roller pair 26 provided downstream of the feedingroller 22 and the separation roller 23 in the feeding direction will nowbe explained. The acceleration roller pair 26 is made up of anacceleration driving roller 24 and an acceleration driven roller 25. Theacceleration driving roller 24 rotates by receiving motive power fromthe second motor 64 (FIG. 3). The acceleration driven roller 25 rotatesas a follower roller when the acceleration driving roller 24 rotates.The acceleration roller pair 26 is an example of a first pair of feedingrollers. The acceleration roller pair 26 further feeds the medium Pdownstream.

The medium feeding path T illustrated in FIG. 2 is curved downwarddownstream of the acceleration roller pair 26. The medium P is fed bythe acceleration roller pair 26 to a resist roller pair 35, which is anexample of a second pair of feeding rollers. The resist roller pair 35is made up of a driving resist roller 35 a and a driven resist roller 35b. The driven resist roller 35 b rotates as a follower roller when thedriving resist roller 35 a rotates. The resist roller pair 35, and otherfeeding rollers provided downstream of the resist roller pair 35, aredriven by a third motor 65 (FIG. 3).

The apparatus has a transportation roller pair 36 that is locateddownstream of the resist roller pair 35. The medium P is turned overwhile it is transported along the curve of the medium feeding path T bythe resist roller pair 35 and the transportation roller pair 36 provideddownstream thereof. The medium P that has been turned over is fed to areading area R1 of the medium feeding path T. The side facing thescanning unit 11 at the reading area R1 of the medium feeding path T ismade of a colorless transparent material, for example, a glass plate.When the medium P passes through the reading area R1, the lower surfaceof the medium P at the reading area R1 is scanned by the reading device16 of the scanning unit 11. Although the illustrated position of thereading device 16 in FIG. 2 is shifted from the reading area R1 in the Ydirection, the reading device 16 is moved to a position corresponding tothe reading area R1 when the medium P transported by the medium feedingapparatus 12 is scanned.

An upper reading device 18 is provided downstream of the reading area R1of the medium feeding path T. The upper reading device 18 is providedover the medium feeding path T. After reading by the reading device 16,the medium P is transported toward the upper reading device 18 byanother transportation roller pair 37. The medium P passes through areading area R2 where scanning is performed by the upper reading device18. During this process, the upper reading device 18 scans the uppersurface of the medium P at the reading area R2. Since the reading device16 and the upper reading device 18 are provided, it is possible to scanboth sides of the medium P.

After reading by the upper reading device 18, the medium P is ejectedonto the ejection tray 39 by an ejecting roller pair 38. The ejectiontray 39 receives the medium P ejected by the ejecting roller pair 38 ina sloped manner.

Control System in Scanner

Next, with reference to FIG. 3, a control system in the scanner 10 willnow be explained. FIG. 3 is a block diagram that illustrates a controlsystem in the scanner 10 according to the present embodiment. In FIG. 3,a control unit 50, which is an example of a controller, performs variouskinds of control on the scanner 10, including feeding control andreading control for the document P and other control. The control unit50 receives signal inputs from the operation unit 6. Signals for displayon the operation unit 6, in particular, signals that realize userinterface (UI), are sent from the control unit 50 to the operation unit6. The control unit 50 controls the first motor 63, the second motor 64,and the third motor 65. As described above, the first motor 63 is adriving source for the pick roller 21 and the feeding roller 22, thesecond motor 64 is a driving source for the separation roller 23 and theacceleration driving roller 24, and the third motor 65 is a drivingsource for the resist roller pair 35 and feeding rollers provideddownstream of the resist roller pair 35. Scan data is inputted from thereading device 16 and the upper reading device 18 to the control unit50. Signals for controlling the reading device 16 and the upper readingdevice 18 are sent from the control unit 50 to the reading device 16 andthe upper reading device 18 respectively. Detection signals are inputtedto the control unit 50 from a size detection unit 57, a first documentdetection unit 58, a multiple feeding detection unit 59, a seconddocument detection unit 60, and a temperature humidity detection unit61. The control unit 50 performs necessary control based on thesedetection signals.

The size detection unit 57 is provided in the feeding tray 20 anddetects the size of the medium P set on the feeding tray 20. The sizedetection unit 57 includes a plurality of sensors that is notillustrated. Specifically, the size detection unit 57 includes aplurality of optical sensors arranged at intervals in the medium feedingdirection and a plurality of optical sensors arranged at intervals inthe medium width direction. A change in detection signals outputted fromthe optical sensors, which constitute the size detection unit 57, occurswhen covered by the medium P set thereon. Based on a combination of thedetection signals of the optical sensors, the control unit 50 detectsthe size of the medium P set on the feeding tray 20.

An example of the positions of the first document detection unit 58, themultiple feeding detection unit 59, and the second document detectionunit 60 is illustrated in FIG. 4. As illustrated in FIG. 4, the firstdocument detection unit 58 is provided near and downstream of thefeeding roller 22 and the separation roller 23. The first documentdetection unit 58 is an optical sensor. Based on a change in a detectionsignal outputted from the first document detection unit 58, the controlunit 50 detects the passing of the leading edge and the trailing edge ofthe document P therethrough. The multiple feeding detection unit 59 isprovided immediately downstream of the first document detection unit 58.The multiple feeding detection unit 59 includes a non-illustratedultrasonic transmitter and a non-illustrated ultrasonic receiver thatare provided in such a way as to face each other, and the documentfeeding path traverses therebetween. An electric signal that indicatesthe intensity of an ultrasonic wave received by the ultrasonic receiveris sent to the control unit 50. The level of the electric signalindicating the intensity of the ultrasonic wave changes if multiplefeeding of the medium P occurs or if there is a change in the thicknessof the medium P. Based on such a change, the control unit 50 is able todetect the occurrence, or non-occurrence, of multiple feeding of themedium P and detect the thickness of the medium P.

The second document detection unit 60 is provided near and upstream ofthe resist roller pair 35. The second document detection unit 60 isanother optical sensor. Based on a change in a detection signaloutputted from the second document detection unit 60, the control unit50 detects the passing of the leading edge and the trailing edge of thedocument P therethrough. The temperature humidity detection unit 61 isprovided in, for example, the feeding tray 20 and detects temperatureand humidity.

Referring back to FIG. 3, the control unit 50 includes a CPU 51, a ROM53, and a memory 54. The CPU 51 performs various kinds of arithmeticprocessing in accordance with a program 52 stored in the ROM 53 andcontrols the entire operation of the scanner 10. The memory 54, which isan example of storage, is a readable and writeable nonvolatile memory. Avariety of data necessary for various kinds of control are stored in thememory 54. In addition, the control unit 50 writes predetermined datainto the memory 54 when necessary.

The scanner 10 is able to get connected to an external computer 70.Information is inputted from the external computer 70 into the controlunit 50. Based on the information transmitted from the external computer70, the control unit 50 performs necessary control.

Next, with reference to FIG. 4 and the subsequent figures, correctingthe skew of the medium P will now be explained. First, a basic methodfor correcting the skew of the medium P will now be explained. In FIG.4, Ta denotes a part of a curved portion of the medium feeding path Talong which the medium P is transported while being curved downward.More specifically, Ta denotes a path section between the accelerationroller pair 26 and the resist roller pair 35. The numerals 40 and 41denote a pair of medium guide members constituting the curved path Ta.The medium guide member 41 has a recess 41 a. The recess 41 a is able toaccommodate a deformed part when the medium P becomes partially deformedoutward. This recessed portion is hereinafter referred to as anaccommodating space 42. The deformed part of the medium P may be namedas a warped part.

After detection of the leading edge of the medium P by the firstdocument detection unit 58, the control unit 50 causes the accelerationroller pair 26 to rotate by a predetermined amount, with the resistroller pair 35 stopped. As a result of this operation, a deformed part Hthat enters the accommodating space 42 is produced in the medium P asillustrated in FIG. 5. Because of the action of the deformed part H, theleading edge Pf of the medium P is pushed against the resist roller pair35. This acts to correct the skew. The deformed part H is a part that isproduced locally only when skew correction is performed, aside from acurve that is formed when the medium P makes its way while being curvedalong the curved path Ta. The foregoing is a basic method for correctingthe skew of the medium P.

With reference to FIG. 10, a technical problem that occurs in astructure that does not include a pushing member described later willnow be explained in detail. As illustrated in the upper part of FIG. 10,the leading edge of the medium P is directed toward the resist rollerpair 35 while being guided along and in contact with the outer guidemember 41 because of the curve of the curved path Ta. After the leadingedge of the medium P reaches the resist roller pair 35, the accelerationroller pair 26 is rotated by a predetermined amount, with the resistroller pair 35 stopped. As a result of this operation, the medium Pclings to the outer guide member 41 of the curved path Ta as illustratedin the lower part of FIG. 10. If the medium P clings to the guide member41 in this way, it becomes harder to rotate the medium P, which isnecessary for skew correction.

To provide a solution to such a problem, in the present embodiment,first, the acceleration roller pair 26 is provided at a center area inthe medium width direction, which is orthogonal to the medium feedingdirection, as illustrated in FIG. 6. In FIG. 6, the deformed part H iscategorized into three areas distinguished from one another as H1, H2,and H3 by their respective positions in the medium width direction. Inthe present embodiment, the deformed part H3 is an area overlapping witha pushing member 43 described later, the deformed part H1 is an arealocated to the left of the deformed part H3 in FIG. 6, and the deformedpart H2 is an area located to the right of the deformed part H3 in FIG.6. In the description below, the deformed parts H1, H2, and H3 arecollectively referred to as the deformed part H when it is unnecessaryto distinguish them from one another.

In FIG. 6, the deformed part that is formed in the medium P during theprocess of skew correction is distinguished into the deformed part H1 atone side and the deformed part H2 at the opposite side in the mediumwidth direction. The degree of deformation of the deformed part H1 atthe side having the leading edge Pf1 of the medium P reaching the resistroller pair 35 earlier is greater than the degree of deformation of thedeformed part H2 at the opposite side. Therefore, the tendency of theabove-described clinging of the medium P to the guide member 41 at theside where the deformed part H1 is formed is greater than that at theside where the deformed part H2 is formed in the medium width direction.In the present embodiment, in order to overcome such a phenomenon, theacceleration roller pair 26 is provided at a center area in the mediumwidth direction, which is orthogonal to the medium feeding direction, asmentioned above. Therefore, the bulge of, in particular, the deformedpart H1, which is more deformed than the deformed part H2, is allowed toescape upstream in the feeding direction as indicated by the arrow Y1from the lateral side of the acceleration roller pair 26. The escapingof the bulge of the deformed part H1 upstream in the feeding directionfrom the lateral side of the acceleration roller pair 26 eliminates theclinging of the medium P to the guide member 41 or reduces the degree ofsuch clinging.

It is the pushing member 43 that fulfills a function of allowing thebulge of the deformed part H1 to escape upstream in the feedingdirection from the lateral side of the acceleration roller pair 26.Specifically, in the present embodiment, the pushing member 43 isprovided in the accommodating space 42. The downstream portion 43 a ofthe pushing member 43 is fixed to the medium guide member 41, which isthe upper guide. The portion located upstream of the downstream portion43 a is able to deform into the accommodating space 42 elastically.

The pushing member 43 pushes the deformed part H3, which is the centerdeformed part of the medium P, upstream in the medium feeding direction.In a cross-sectional view, the pushing member 43 pushes the deformedpart H3 of the medium P in the direction indicated by the arrow E inFIG. 5. The pushing force acting in the direction indicated by the arrowE includes a force component of separating the deformed part H3 from themedium guide member 41 and a force component of pushing the deformedpart H3 upstream in the feeding direction. Since the pushing member 43pushes the deformed part H3 in the direction of separation from themedium guide member 41 and upstream in the feeding direction, at thedeformed part H1, the bulge is allowed to escape in the directionindicated by the arrow Y1 in FIG. 6. The escaping of the bulgeeliminates the clinging of the medium P at its deformed part H1 to theguide member 41 or reduces the degree of such clinging. Therefore, itbecomes easier to rotate the medium P, which is necessary for skewcorrection. That is, in the illustrated example, it becomes easier torotate the medium P in the direction indicated by the arrow r in FIG. 6.The rotation causes the leading edge Pf2 of the medium P at the sidethat is behind in transportation to advance properly toward the resistroller pair 35 as indicated by the arrow Y2 in FIG. 6. Therefore, theskew is corrected well.

The directional force of pushing the medium P, which results frompushing the deformed part H3 of the medium P by the pushing member 43,is split into directional components indicated by the arrows E21, E22,and E23 in FIG. 6. The directional component indicated by the arrow E21acts to allow the bulge of the deformed part H1 to escape upstream asdescribed above. The directions indicated by the arrows E22 and E23 aredirections of bringing the leading edge of the medium P into abutmentagainst the resist roller pair 35. Although these directional componentstherefore act in such a way as to cause the medium P to cling to theguide member 41 otherwise, the above-described layout of theacceleration roller pair 26 and the above-described function of thepushing member 43 prevent the clinging of the medium P to the guidemember 41 from occurring or reduce the degree of such clinging.

In the present embodiment, segments of the acceleration roller pair 26are provided at positions that are symmetric with respect to the centerin the medium width direction. The description “the acceleration rollerpair 26 is provided at a center area in the medium width direction” isnot necessarily limited to a structure in which the acceleration rollerpair 26 is located at the center in the medium width direction.Specifically, the description “the acceleration roller pair 26 isprovided at a center area in the medium width direction” encompasses notonly such a structure but also a structure in which a segment of theacceleration roller pair 26 is provided at one side and a segment of theacceleration roller pair 26 is provided at the opposite side, with thecenter located between the segment at the one side and the segment atthe opposite side in the medium width direction.

In the present embodiment, the pushing member 43 is an elastic memberwhose downstream portion in the medium feeding direction is fixed andwhose upstream portion in the medium feeding direction pushes thedeformed part H of the medium P. Although any member that is able todeform due to its elastic property can be used as such an elasticmember, a preferred example is a member that is made of a material thathas a low coefficient of friction with the medium P and is notobstructive to the rotation of the medium P, such as polyethyleneterephthalate (PET). Since the pushing member 43 is made of an elasticmaterial, it is possible to push the deformed part H of the medium Pupstream in the medium feeding direction properly.

The pushing member may be a member that has a pivot structure asillustrated in FIG. 7. A pushing member 44 illustrated in FIG. 7 has apivot 44 a near its downstream end in the medium feeding direction. Thebody located upstream of the pivot 44 a in the medium feeding directionserves as a pivot member that pushes the deformed part H of the mediumP. The upstream portion of the pushing member 44 is urged by a spring45. The modified structure described here also makes it possible to pushthe deformed part H of the medium P upstream in the medium feedingdirection properly.

The pushing member may be, for example, a member like a piston thatadvances toward and retreats from the deformed part H, instead of amember that has a pivot structure. For example, a solenoid that isswitchable between a current-applied state and a non-applied state maycause such a piston to advance toward and retreat from the deformed partH under the control of the control unit 50. The piston may be usually ina retreated position away from the curved path Ta and may advance towardthe curved path Ta and push the deformed part H under the control at thesame time as the producing of the deformed part H or after the producingof the deformed part H.

In the present embodiment, the pushing member 43 is provided at a centerarea in the medium width direction as illustrated in FIG. 6. This layoutmakes it easier for the force of pushing the medium P by the pushingmember 43 to equally act at one side and the opposite side in the mediumwidth direction and thus makes it possible to correct the skew properlyeven if it is not predictable which one of the two in the medium widthdirection will be the side where the degree of deformation is greater.The description “the pushing member 43 is provided at a center area inthe medium width direction” is not necessarily limited to a structure inwhich the pushing member 43 is located at the center in the medium widthdirection. This description encompasses not only such a structure butalso a structure in which a segment of the pushing member is provided atone side and a segment of the pushing member is provided at the oppositeside, with the center located between the segment at the one side andthe segment at the opposite side in the medium width direction.

Although the pushing member is provided at a center area in the mediumwidth direction in the present embodiment, the pushing member may have asize that is large enough for the entire area in the medium widthdirection.

The control unit 50 configured to control the acceleration roller pair26 and the resist roller pair 35 may change an amount of driving theacceleration roller pair 26 depending on feeding conditions when theacceleration roller pair 26 is driven, with the resist roller pair 35stopped. The drive amount corresponds to an amount of bringing theleading edge of the medium P into abutment against the resist rollerpair 35. Therefore, the drive amount is hereinafter referred to as“abutment amount”.

The feeding conditions may include, for example, the speed of feedingthe medium P by the acceleration roller pair 26, the size of the mediumP, the thickness of the medium P, and temperature and humidity. It ispossible to set the abutment amount depending on these feedingconditions. Table 1 shows an example of abutment amount addition valuesthat depend on the feeding speed. Table 2 shows an example of abutmentamount addition values that depend on the size of the medium P. Table 3shows an example of abutment amount addition values that depend ontemperature and humidity and the thickness of the medium P.

For example, an addition value “6” is obtained from Table 1 when thefeeding speed is “high”. An addition value “−2” is obtained from Table 2when the size of the medium P is “A5 landscape”. An addition value “1”is obtained from Table 3 when the temperature/humidity condition is that“temperature T: 1° C. or lower, and humidity S: higher than 1%” and whenthe thickness of the medium P is “thick”. In this example, it ispossible to calculate the abutment amount (mm) as follows: abutmentamount (mm)=“6”+“−2”+“1”=5 (mm). The size of the medium P shown in Table2 is A-series paper size and B-series paper size set forth in ISO 216,which is an international standard.

As explained above, the control unit 50 configured to control theacceleration roller pair 26 and the resist roller pair 35 changes theamount of driving the acceleration roller pair 26 depending on thefeeding conditions when the acceleration roller pair 26 is driven, withthe resist roller pair 35 stopped, that is, switches the abutmentamount. Therefore, it is possible to correct the skew suitably inaccordance with the feeding conditions.

TABLE 1 Feeding speed High Low 6 4

TABLE 2 A5 Landscape B5 Landscape B5 Portrait B4 Portrait A4 LandscapeA4 Portrait A3 Portrait −2 0 −1

TABLE 3 Temperature Humidity/Sheet thickness T: 1° C. or lower T: Higherthan 1° C. S: 1% or lower Thin 0 0 Thick 1 1 S: Higher than Thin 0 −2 1%Thick 1 0

With reference to FIG. 8, the flow of feeding control performed by thecontrol unit 50 will now be explained. Upon receiving a medium feedinginstruction (step S11), the control unit 50 acquires information on thesize of the medium P (step S12) and information on temperature andhumidity (step S13) and then starts feeding the medium P (step S14).When the leading edge of the medium P reaches the multiple feedingdetection unit 59 after starting the feeding of the medium P, thecontrol unit 50 acquires information on the thickness of the medium P(step S15) and calculates an abutment amount depending on the feedingconditions (step S16). Based on the calculated abutment amount, theleading edge of the medium P is brought into abutment against the resistroller pair 35 for skew correction (step S17). The feeding operationfurther continues, and the medium P is fed to the reading position andis read thereat (step S18) In the above feeding control, the skew of themedium P is properly corrected because of the action of the pushingmember 43 described above.

What is claimed is:
 1. A medium feeding apparatus, comprising: a firstpair of feeding rollers configured to feed a medium downstream; a secondpair of feeding rollers provided downstream of the first pair of feedingrollers; a curved path that is a medium feeding path formed between thefirst pair of feeding rollers and the second pair of feeding rollers,the medium being transported along the curved path while being curveddownward; and an accommodating portion formed outside a curve of thecurved path and configured to accommodate a deformed part of the mediumat the curved path; wherein the first pair of feeding rollers isprovided at a center area in a medium width direction intersecting witha medium feeding direction, and wherein the accommodating portion has apushing member configured to push the deformed part of the mediumupstream in the medium feeding direction.
 2. The medium feedingapparatus according to claim 1, wherein the pushing member is an elasticmember whose downstream portion in the medium feeding direction is fixedand whose upstream portion in the medium feeding direction pushes thedeformed part of the medium.
 3. The medium feeding apparatus accordingto claim 1, wherein the pushing member is a pivot member that has apivot at a downstream portion in the medium feeding direction, and anupstream portion located upstream of the pivot in the medium feedingdirection pushes the deformed part of the medium.
 4. The medium feedingapparatus according to claim 1, wherein the pushing member is providedat a center area in the medium width direction.
 5. The medium feedingapparatus according to claim 1, further comprising: a controllerconfigured to control the first pair of feeding rollers and the secondpair of feeding rollers; wherein the controller changes an amount ofdriving the first pair of feeding rollers depending on feedingconditions when the first pair of feeding rollers is driven, with thesecond pair of feeding rollers stopped.
 6. An image reading apparatus,comprising: a reader configured to read a medium; and the medium feedingapparatus according to claim 1 configured to feed the medium toward areading position where the medium is read by the reader.